Obsoleted ParsedInstance.start/end_time attributes, since they no longer perform a useful function given the implementation of instanceIDs, yet they were causing db sync problems (legacy xml data submissions affected by this bug -- https://github.com/SEL-Columbia/formhub/issues/1206 -- were raising timezone based ValueErrors during the sync process between mysql and mongodb).
Merge pull request #1296 from SEL-Columbia/fix-ParsedInstance-legacy-tz

Obsoleted ParsedInstance.start/end_time attributes, since they no longer...